gecko/gfx/layers/LayerUtils.cpp

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/* -*- Mode: c++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
#include "LayerUtils.h"
#include "PremultiplyTables.h"
#include "mozilla/Endian.h"
namespace mozilla {
namespace layers {
using namespace mozilla::gfx;
static inline const uint8_t PremultiplyValue(uint8_t a, uint8_t v) {
return PremultiplyTable[a*256+v];
}
static inline const uint8_t UnpremultiplyValue(uint8_t a, uint8_t v) {
return UnpremultiplyTable[a*256+v];
}
#ifdef DEBUG
static bool IsLittleEndian()
{
// Violate strict aliasing, because violating strict aliasing is how
// we always pack and unpack between uint32_t and uint8_t[].
uint16_t testShort;
static const uint8_t testBytes[2] = { 0xAA, 0xBB };
memcpy(&testShort, testBytes, sizeof(testBytes));
return testShort == 0xBBAA;
}
#endif // DEBUG
#ifdef MOZ_LITTLE_ENDIAN
#define ASSERT_ENDIAN() MOZ_ASSERT(IsLittleEndian(), "Defined as little endian, but actually big!")
#else
#define ASSERT_ENDIAN() MOZ_ASSERT(!IsLittleEndian(), "Defined as big endian, but actually little!")
#endif
void
PremultiplySurface(DataSourceSurface* srcSurface,
DataSourceSurface* destSurface)
{
if (!destSurface)
destSurface = srcSurface;
IntSize srcSize = srcSurface->GetSize();
MOZ_ASSERT(srcSurface->GetFormat() == destSurface->GetFormat() &&
srcSize.width == destSurface->GetSize().width &&
srcSize.height == destSurface->GetSize().height &&
srcSurface->Stride() == destSurface->Stride(),
"Source and destination surfaces don't have identical characteristics");
MOZ_ASSERT(srcSurface->Stride() == srcSize.width * 4,
"Source surface stride isn't tightly packed");
// Only premultiply ARGB32
if (srcSurface->GetFormat() != SurfaceFormat::B8G8R8A8) {
if (destSurface != srcSurface) {
memcpy(destSurface->GetData(), srcSurface->GetData(),
srcSurface->Stride() * srcSize.height);
}
return;
}
uint8_t *src = srcSurface->GetData();
uint8_t *dst = destSurface->GetData();
// Assert that our endian define is correct.
ASSERT_ENDIAN();
uint32_t dim = srcSize.width * srcSize.height;
for (uint32_t i = 0; i < dim; ++i) {
#ifdef MOZ_LITTLE_ENDIAN
uint8_t b = *src++;
uint8_t g = *src++;
uint8_t r = *src++;
uint8_t a = *src++;
*dst++ = PremultiplyValue(a, b);
*dst++ = PremultiplyValue(a, g);
*dst++ = PremultiplyValue(a, r);
*dst++ = a;
#else
uint8_t a = *src++;
uint8_t r = *src++;
uint8_t g = *src++;
uint8_t b = *src++;
*dst++ = a;
*dst++ = PremultiplyValue(a, r);
*dst++ = PremultiplyValue(a, g);
*dst++ = PremultiplyValue(a, b);
#endif
}
}
}
}